This invention relates to a method for producing an endless reinforced toothed belt from synthetic plastic material or the like with embedded force-transmission elements of wire or thread form extending in the longitudinal direction of the belt. A mould cavity is formed between a rotatable moulding wheel having an annular channel upon its circumference corresponding to the belt cross-section and a covering closes the channel over a part of the circumference of the moulding wheel. The plasticized synthetic plastic material is introduced into the beginning of the mould cavity which is closable by an injection nozzle. The invention further relates to an apparatus for carrying out the above-mentioned method.
With the apparatus and method according to Federal Republic of Germany Pat. No. 2,123,902 which utilizes a rotatable moulding wheel and as covering an endless moulding band advancing with the moulding wheel, a reinforced toothed belt can be produced which, however, is finite and must be made endless for use as a circulating drive element between toothed wheels so that the toothed belt has an interruption of its embedded force-transmission elements at the point of the circumference where the endless connection takes place. With the method and apparatus known for example from Federal Republic of Germany Pat. No. 2,526,691 which, in addition to a moulding wheel and moulding band uses an axially parallel tensioner wheel remote from the moulding wheel, an endless reinforced toothed belt can be produced, the desired circumferential length of which can be varied by variation of the axial distance between moulding wheel wheel and tensioner wheel. However, the minimum circumferential length which can be produced, which is dependent upon the diameter of the moulding wheel and of the tensioner wheel, is limited by the minimum possible axial distance down to which the tensioner wheel can approach the moulding wheel. Below this minimum circumferential length in fact it is possible to produce endless reinforced toothed belts with what is called tool-confined belt circumferential length in a moulding tool known, for example, from Federal Republic of Germany Pat. No. 2,653,741 and consisting of a mould core and a moulding sleeve. However, for every belt size to be produced, a separate extension moulding tool, to be manufactured complete from mould core and moulding sleeve, is necessary.
The invention has faced the problem of further developing a production method of the initially stated classification in such a way that endless reinforced toothed belts can be produced, the belt circumferential length of which is smaller than the minimum circumferential length which can be produced with a method after the style of Federal Republic of Germany Pat. No. 2,526,691, and can be varied to be as much greater as desired as from a ring size corresponding substantially to the circumference of the utilized moulding wheel.